Quantitative Changes of Phenolic Compounds in Pine Twigs by Variety, Harvest Season, and Growing Region

Three new phenolic compounds including pinosylvin 3-methoxy-5-O-β-D-glucoside (PMG), taxiresinol 4’-O-α-L-rhamnoside (TRR), and lariciresinol 4’-O-α-L-rhamnoside (LRR) were first isolated and identified from red pine (Pinus densiflora Sieb. et Zucc.) twigs, together with four known compounds, such as (+)-catechin (CC), dihydromyricetin (DHM), dihydroquercetin 3-O-β-D-glucoside (DHQG), and dihydroquercetin (DHQ). Additionally, the concentrations of seven phenolic compounds in pine twigs were measured by high-performance liquid chromatography based on cultivars, harvest seasons, and growing environments. Red and black pine twigs contain 379.33 and 308.83 mg/100 g of PMG as the predominant phenolics, respectively, and their contents were significantly higher in spring than in autumn. Red pine twigs contain higher amounts of three dihydroflavonols (DHM: 87.82, DHQG: 38.47, and DHQ: 68.07 mg/100 g) and two lignans (LRR: 15.63, TRR: 30.72 mg/100 g) than black pine twigs, except for higher (+)-CC level (21.88 mg/100 g) in black pine twigs. Two pine twigs had much higher flavonoid and lignan levels in the autumn than they had in the spring. Two pine twigs harvested in several different areas do not significantly differ in their phenolic compositions and contents. These results suggest that red pine twigs possessing phytochemical phenolics may be useful as potential sources for promoting human health.